The present invention generally relates to wireless communication networks, and particularly relates to carrying backhaul traffic on the in-band air interface utilized by such networks.
Wireless communication networks generally include one or more Radio Access Networks (RANs) that provide access to the network. The RAN includes the transceiver resources and associated processing required for supporting radio communication with mobile stations, such as radiotelephones. A typical RAN includes a base station controller and a plurality of radio base stations (RBSs) that serve as access points (APs) for mobile stations. The base stations transmit communication traffic and control data to mobile stations on a forward radio link, and receive communication traffic and control signaling from the mobile stations on a reverse radio link. The frequencies, timing, structure, modulation, and other characteristics of such radio links are governed by the particular “air interface” adopted by the wireless network.
The BSC supervises the operation of the base stations and interfaces the RAN with a core network (CN), which communicatively couples the RAN to the Public Switched Telephone Network (PSTN) and to external Packet Data Networks (PDNs), such as the Internet. The CN may include both circuit-switched and packet-switched communication entities supporting both circuit-switched and packet-switched communication traffic being carried to and from the mobile stations supported by the RAN.
The radio base stations do not use the mobile station air interface for communication with the supporting BSC. Rather, such communication links, generally referred to as “backhaul” links, rely on relatively high bandwidth dedicated communication links, such as T1/E1 lines and/or microwave relay stations. The structure, synchronization, data formats, and signaling protocols differ significantly between the backhaul links and the air interface radio links. Incoming traffic from the core network destined for one or more mobile stations is reformatted for radio transmission according to the requirements of the air interface, and outgoing traffic received from the mobile stations is reformatted for transmission according to the protocol(s) established for the backhaul links.
While dedicated backhaul links provide the bandwidth and reliability needed to carry the aggregate traffic and control signaling passing through the RAN, they impose potentially significant economic and physical barriers to the initial deployment of new wireless networks or the expansion of existing ones. Such barriers arise from, for example, the expense and difficultly of installing land-based backhaul communication links to each of the radio base stations in a RAN. As such radio base stations typically are arranged in a distributed “cellular” pattern, dedicated backhaul links must be installed for each cell.
In poorer countries, such installation may not be practical because of cost constraints, or because the labor and materials necessary for such installation simply are lacking. Even where cost is not the overriding concern, the terrain may be too rugged, or the network operator may need to become operational more quickly than would be practical with land-line construction delays. While microwave links overcome some of the construction difficulties, microwave-based solutions still present technological difficulties, and do nothing to reduce expenses.
Thus, the conventional approach to backhaul interconnection in wireless communication networks can, in some circumstances, unnecessarily delay network deployment and significantly increase the costs of such deployment. Under certain operational conditions, such as where one or more cells in the network are relatively lightly loaded, a different, lower cost backhaul interconnection might be adopted such that deployment costs and complexity are reduced.